# Claude Opus 5.5 vs Llama 3.1-405B

> Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 30.7 on the Noometry Index.

- Canonical page: https://noometry.com/compare/claude-opus-5-5-vs-llama-3-1-405b
- Last updated: 2026-10-10
- Shared benchmarks: 19

## Summary

- They share 19 benchmarks with published results for both. Claude Opus 5.5 scores higher in 9 categories and Llama 3.1-405B in 0 categories; 9 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Opus 5.5 leads 91.8 to 18.4.
- The biggest single-benchmark swing is OTIS Mock AIME 2024-2025: 100% for Claude Opus 5.5 and 9.7% for Llama 3.1-405B.
- Llama 3.1-405B has downloadable open weights; the other is API-only.

## Snapshot

| | Claude Opus 5.5 | Llama 3.1-405B |
|---|---|---|
| Provider | Anthropic | Meta |
| Noometry Index | 68.6 | 30.7 |
| Rank | 3 | 288 |
| Context | 1M | — |
| Input $/M | $4 | — |
| Output $/M | $20 | — |
| Weights | Proprietary | Open |

## Coding

- Claude Opus 5.5: 71.9 (#3)
- Llama 3.1-405B: 33.1 (#262)

| Benchmark | Claude Opus 5.5 | Llama 3.1-405B |
|---|---|---|
| LMArena Coding | 1547 | 1291 |
| FrontierCode | 54.6% | — |
| CursorBench | 57.8% | — |
| LMArena WebDev | 1813 | — |
| FrontierSWE | 62.3% | — |
| SciCode | 66.9% | — |
| WeirdML | — | 21.4% |
| MirrorCode | 77.4% | — |
| ALE-Bench | 2,147 | — |

## Agentic & Tool Use

- Claude Opus 5.5: 45.3 (#15)
- Llama 3.1-405B: 21.0 (#140)

| Benchmark | Claude Opus 5.5 | Llama 3.1-405B |
|---|---|---|
| APEX-Agents | 73.5% | — |
| TheAgentCompany | — | 7.4% |
| Cybench | — | 7.5% |
| GDP.pdf | 30.6% | — |
| Vending-Bench 2 | 9,235 | — |

## Reasoning

- Claude Opus 5.5: 80.2 (#3)
- Llama 3.1-405B: 16.8 (#300)

| Benchmark | Claude Opus 5.5 | Llama 3.1-405B |
|---|---|---|
| LMArena Hard Prompts | 1535 | 1269 |
| DTBench | 98.9% | 61.4% |
| Epoch Capabilities Index | 167.33 | 128.75 |
| ARC-AGI-2 | 93.3% | — |
| SimpleBench | — | 23% |
| Kagi LLM Benchmark | — | 45% |
| NYT Connections (extended) | 88.5% | — |
| ARC-AGI-1 | 98.5% | — |
| CritPt | 31.7% | — |
| EBR-Bench | 71.4% | — |
| Mystery Game Puzzles | 71% | — |
| LMCA | 68.2% | — |
| BIG-Bench Hard | — | 82.9% |
| ForecastBench | — | 59.9 |
| HellaSwag | — | 89.2% |
| PIQA | — | 85.9% |
| WinoGrande | — | 89.2% |

## Math

- Claude Opus 5.5: 91.8 (#3)
- Llama 3.1-405B: 18.4 (#290)

| Benchmark | Claude Opus 5.5 | Llama 3.1-405B |
|---|---|---|
| OTIS Mock AIME 2024-2025 | 100% | 9.7% |
| LMArena Math | 1506 | 1281 |
| FrontierMath (Tiers 1-3) | 91.2% | — |
| FrontierMath Tier 4 | 95% | — |
| ProofBench | 100% | — |
| Omni-MATH | — | 24.9% |
| MATH Level 5 | — | 49.8% |
| FrontierMath Erdős | 2.9% | — |

## Knowledge

- Claude Opus 5.5: 66.4 (#10)
- Llama 3.1-405B: 30.4 (#227)

| Benchmark | Claude Opus 5.5 | Llama 3.1-405B |
|---|---|---|
| GPQA Diamond | 90.6% | 50.9% |
| LMArena Expert | 1547 | 1243 |
| SimpleQA Verified | 72.2% | — |
| MMLU-Pro | — | 72.3% |
| Confabulations | — | 17.6% |
| GPQA (HELM) | — | 52.2% |
| ARC (AI2) Challenge | — | 95.3% |
| MMLU | — | 84.5% |
| TriviaQA | — | 82.7% |

## Multimodal

- Claude Opus 5.5: 57.8 (#1)
- Llama 3.1-405B: —

| Benchmark | Claude Opus 5.5 | Llama 3.1-405B |
|---|---|---|
| LMArena Vision | 1321 | — |
| Blueprint-Bench 2 | 51.2% | — |
| Furniture Assembly | 83.3% | — |

## Multilingual

- Claude Opus 5.5: 59.1 (#2)
- Llama 3.1-405B: 40.7 (#214)

| Benchmark | Claude Opus 5.5 | Llama 3.1-405B |
|---|---|---|
| LMArena Non-English | 1507 | 1248 |
| LMArena Chinese | 1588 | 1242 |
| LMArena French | 1514 | 1279 |
| LMArena Russian | 1520 | 1265 |
| LMArena Spanish | 1507 | 1260 |
| LMArena German | — | 1252 |
| LMArena Japanese | — | 1208 |
| LMArena Korean | — | 1184 |

## Instruction Following

- Claude Opus 5.5: 80.0 (#3)
- Llama 3.1-405B: 65.9 (#214)

| Benchmark | Claude Opus 5.5 | Llama 3.1-405B |
|---|---|---|
| LMArena Instruction Following | 1537 | 1259 |
| IFEval | — | 81.1% |

## Long Context

- Claude Opus 5.5: 47.1 (#19)
- Llama 3.1-405B: 38.4 (#197)

| Benchmark | Claude Opus 5.5 | Llama 3.1-405B |
|---|---|---|
| LMArena Longer Query | 1532 | 1266 |

## Writing & Preference

- Claude Opus 5.5: 78.2 (#3)
- Llama 3.1-405B: 38.9 (#251)

| Benchmark | Claude Opus 5.5 | Llama 3.1-405B |
|---|---|---|
| LMArena Text | 1515 | 1284 |
| LMArena Creative Writing | 1533 | 1262 |
| EQ-Bench Creative Writing | 2050 | 870 |
| LMArena Multi-Turn | 1499 | 1297 |
| WildBench | — | 78.3% |

## FAQ

### Is Claude Opus 5.5 better than Llama 3.1-405B?

Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 30.7 on the Noometry Index.

### Is Claude Opus 5.5 or Llama 3.1-405B better for coding?

Claude Opus 5.5 scores higher on coding benchmarks: 71.9 versus 33.1 in the Noometry coding category.

### How many benchmarks do Claude Opus 5.5 and Llama 3.1-405B share?

19 benchmarks have published results for both models. Claude Opus 5.5 has 44 scored results on Noometry and Llama 3.1-405B has 42.